1. Field of the Invention
The present invention relates to semiconductor substrate processing equipment. More particularly, the present invention relates to methods and apparatuses wherein a substrate is clamped to a support member with a clamp ring, and the deposition layer may form a bridging deposit between the clamp ring and the substrate surface. More particularly still, the present invention provides methods and apparatuses for detaching a substrate from a ring when the deposition material forms a bridging film layer between the substrate and an adjacent chamber component such as a clamp ring, without causing significant damage to the substrate. Further, the present invention provides methods and apparatuses for detaching a substrate having minimal moving parts which slide, rub or engage each other near the substrate surface.
2. Background of the Art
The fabrication of semiconductor devices on substrates, including semiconductor substrates, typically requires the deposition of multiple metal, dielectric and semiconductor film layers on the surface of the substrate. The film layers are typically deposited on the substrates in vacuum chambers. One deposition process is sputtering, wherein a target comprised of the deposition material is exposed to a plasma and atoms or larger particles of target material are sputtered from the target and are deposited on the substrate. An additional example of a deposition process is chemical vapor deposition, wherein a chemical vapor is exposed to the substrate and a film layer of the vapor components may be formed on the substrate.
To support the substrate in the chamber, a support member, commonly a susceptor or a pedestal, is located in the chamber. The substrate is placed on, and secured to, the upper surface of the support member during the deposition process.
To form the deposition layer on the substrate, a deposition environment must be created within the chamber adjacent to the deposition receiving surface of the substrate. In a chemical vapor deposition chamber, the deposition environment is a chemical vapor which, when contacted with the substrate, deposits onto the substrate to form the deposition layer. In a physical vapor deposition system, the deposition environment includes a plasma maintained between a target and the deposition receiving surface of the substrate and a flux of sputtered target particles passing between the target and the deposition receiving surface of the substrate. A portion of the sputtered target particles deposit on the substrate to create the deposition layer.
In both the chemical vapor deposition and physical vapor deposition systems, the deposition material will, if left unconfined, deposit on all of the interior surfaces of the chamber. Therefore, shield arrangements have been devised to restrict the deposition environment to a region adjacent to the deposition receiving surface of the substrate. The shield system typically includes a fixed wall portion which extends between the chamber cover and the position within the chamber where the pedestal is positioned during the deposition of the film. The fixed wall portion extends around the circumference of the support member when the support member is positioned for the deposition, and it thus blocks access of the deposition environment to the walls and interior components of the chamber. However, a small gap must be provided between the support member and the shield, to allow the support member to retract and extend in the chamber without the risk of the support member contacting the fixed wall portion.
The gap between the inner terminus of the fixed wall portion and the support member provides a path for deposition material to enter the regions of the chamber which are protected by the fixed wall portion and deposit an undesirable film layer on these surfaces. Therefore the gap is covered, typically by placing an annular ring over the gap. The ring is commonly known as a clamp ring, because it can also serve as the means for securing the substrate to the support member. To enable heat transfer between the support member and the substrate, the substrate must be firmly chucked to the support member. One means of chucking is to physically "clamp" the substrate to the support member by virtue of the weight of the clamp ring. The clamp ring typically includes a lip, which extends inwardly of the support member and over the edge of a substrate received on the support member. The lip is sized to extend inwardly over the substrate by a distance which is sufficient to block access of the deposition material to the substrate edge below the lip and from the juncture of the clamp ring with the support member, and is further sized to provide a small space between the underside of the lip and the upper surface of the substrate. Without the lip, deposition material could form a bridging layer between the edge of the substrate and the support member which could interfere with the easy removal of the substrate from the support member.
Although the clamp ring with the overhanging lip prevents the formation of a film layer between the substrate and the pedestal, deposition material may still deposit on the inner edge and underside of the lip and eventually bridge the space between the upper surface of the substrate and the lip. This bridging film layer may be strong enough to attach the substrate to the clamp ring, in which case the chamber must be shut down to remove the substrate and the entire substrate will be rendered worthless. In the worst case, the substrate may maintain an attachment to the clamp ring for only a short period of time, after which it falls in the chamber. In that case, the chamber components might also be damaged. To prevent this, the clamp ring must be periodically replaced with a clean clamp ring on a regular maintenance schedule. However, on occasion a bridging deposition material layer may still form between the substrate and the lip.
In co-pending application Ser. No. 08/358,161, a clamp ring is described for shielding a substrate during film layer deposition. This ring includes a biasing member to separate the substrate from the clamp ring if a bridging film layer has formed between the clamp ring and the substrate during processing. One potential limitation of this design may be the location of moving parts above the substrate, which might create particles above the surface of the substrate which could then fall onto, and contaminate a substrate. Additionally, if anti-stick mechanisms have tangential movement to free the substrate from the ring, such as where the rocker arm pushes a substrate from the ring, the mechanism may move along the surface of the substrate a short distance, thereby "scratching" the substrate and generating particles. Finally, if the clamp ring is provided with a member to physically push the substrate therefrom, a hood must typically be provided to receive the member, and the hood may physically block line of sight access between the substrate and portions of the target, thereby shadowing the substrate. Although this design provides a significant improvement over clamp rings where no means is provided to ensure separation of the substrate from the clamp ring, there still exists a need for a clamp (or shield) arrangement that will provide shielding of the substrate edge while further eliminating, or substantially reducing, the risk of damage to the substrate resulting from substrate attachment to the clamp ring, and while reducing the likelihood of particle generation in the chamber. The present invention provides methods and apparatuses for solving substrate "sticking" problems and/or related particle concerns in physical vapor deposition (PVD) chambers or other film layer deposition chambers.